The Two Nancys Tour of Western National Parks

Last month, I decided to visit and take amateur photographs of National Parks. This May, after talking with a girlfriend (another Nancy), a decision was made to visit the Grand Canyon, Bryce and Zion. So the two Nancys headed west, May 2021.

As we visited each park, we started to wonder about their geology and how they came about. Each National Park is beautifully unique and awe inspiring.

These parks are geologically associated with one another and are the result of a combination of distinctive geologic events (sedimentation, lithification, erosion, volcanic and tectonic uplifting ). Today, these forces continue to work on the Canyons. The below information is a paraphrase of the referenced information. Click on these hyperlinks for more detail

Click here for the geology of the Grand Canyon informatio

Click here for the geology of Bryce Canyon information

Click here for the geology of Zion information

The Colorado Plateau is a region in the Southwest USA. About 50 million years ago, the Colorado Plateau was mostly flat and part of a lake and floodplain system. The Colorado Plateau encompasses parts of the Four Corners region (Utah, Colorado, Arizona, and New Mexico). This area includes parks such as the Grand Canyon, Arches National Park, Canyonlands, Mesa Verde, and Bryce Canyon. Zion National Park is located along the edge of the Colorado Plateau, sitting at the boundary between the Basin and Range geologic province and the Colorado Plateau.

Today, due to tectonic activity, “The Colorado Plateau is at a higher elevation than its surroundings, ranging from about 2000 -12,000 feet above sea level at its highest peaks. While some of the lowest (oldest) rocks in the region are metamorphic and igneous, the more visible and characteristic rocks are layered, sedimentary rocks with vibrant hues of rust-colored reds and orange.”

Through a series of volcanic action, tectonic uplifts and erosion the bottom layer of rock at Bryce Canyon is the top layer at Zion, and the bottom layer at Zion is the top layer at the Grand Canyon. Interesting concept, isn’t it?

The Grand Canyon came into being when igneous and metamorphic rocks were formed about 2 billion years ago and layer upon layer of sedimentary rocks were laid on top of these basement rocks. Between 70 and 30 million years ago the whole region was uplifted, resulting in the high and relatively flat Colorado Plateau.

Finally, beginning just 5-6 million years ago, the Colorado River began to carve its way downward through the sedimentary rock.

Bryce Canyon is known for its distinctive hoodoos, spires and towers. To me these towers resemble castles and cathedrals. Others see them as forests of rock.

Millions of years ago, the Colorado Plateau, in which Bryce resides, was once periodically flooded by freshwater. Bryce Canyon is almost entirely composed of sedimentary rocks, meaning it was formed by deposits of sediments (precipitated out of water) cemented together (lithified) into sedimentary rock and later uplifted by tectonic activity. Over time, the rock was subjected to the slow, powerful weathering and erosion forces that molded the columns seen today.

Zion was a relatively flat basin near sea level 240 million years ago. Sedimentation of mountain runoff deposits, lithification, volcanic activity, tectonic uplift, erosion and the Virgin River carved out the current Canyon. Today, uplift is still occurring. In 1992, Springdale (city at the south park entrance) had a 5.8 earthquake and the Virgin River is still excavating. The canyon is subject to powerful flash floods.